Industrial sites such as chemical, petrochemical, oilfields, coalmines and the like often are scattered or stocked with gases, dust or chemicals that are inflammable, easily exploded or oxidized, or corrosive. Hence lamps used on those sites must be explosion-proof to avoid explosion incident caused by sparks that might be generated by worn out or faulty general non explosion-proof lamps.
In those potentially explosive environments the explosion-proof lamp often provides a limited projection range, as a result there are always some blind spots falling outside of the projection range of the explosion-proof lamp. Hence many more explosion-proof lamps must be installed, or multiple sets of explosion-proof lamps have to be connected in series to overcome the problem of non-illuminating blind spots. The conventional approach of connecting the explosion-proof lamps is done via a connection set. More connection sets are required when more explosion-proof lamps are to be connected together. This makes the cost higher and consumer's purchasing desire lower.
To solve the problem of relying on extra connection sets for serial connection of explosion-proof lamps that occurs to the conventional practice, another technique has been proposed as shown in FIG. 1, in which two sets of explosion-proof lamps A1 that are to be coupled together can be accomplished by providing a connection dock A2 on each explosion-proof lamp A1, and fastening the two connection docks A2 together through a plurality of screws B1. However, the screws B1 are exposed outside the connection docks A2, it is not appealing in appearance and makes consumers reluctant to buy. There are still rooms for improvement.